The use of biologically generated reference substances would be studied in this research, with an emphasis on detection of isotopically labeled analytes. In our preliminary work dual-label methods have been shown to be useful with biogenic standards. However, the technique needs further development, and would be extended to stable isotopes. Biogenic standards have advantages over pure homogeneous reference materials, since they can be produced inexpensively and can yield substances for which economic synthesis techniques have not been developed. Furthermore, use of several biogenic standards could be used concurrently and would not require compound identification in order to produce useful results in experiments. Moreover, they allow for sensitive tests for effects of impurities, isotope exchange or isotope-caused kinetic differences. In the proposed research, dual-label radiochemical methods would be employed to investigate uses of biogenic standards in complex reaction systems. Metabolism studies would be used as models of complex reactions and comparisons between control vs. test rapist groups will be investigated. The early investigations would use polynuclear aromatic hydrocarbons and aromatic heterocyclic compounds as study substances. Later studies would use dual-label detection by mass spectrometry to adopt 2H and 13C labeling for use with biogenic standard methods.